Ocular melanoma is the most common primary intraocular malignancy in adults and comprises over 50% of all malignancies of the eye. Unfortunately, he optimal therapy for the effective management of ocular melanoma is still unclear. We plan to perform preclinical studies to evalute the applications of Hematoporphyrin Photoradiation Therapy in treating ocular melanoma. Hematoporphyrin derivative (HpD) is a drug which has been shown to exhibit properties of both preferential tumor localization and visible light activateed tumor destruction via photosensitization. Since this therapy has already been proven in the clinic to be effective in eradicating a variety of superficial malignant lesions while inducing only minimal normal tissue dmage, it is possible that his modality may be useful in treating intraocular tumors. The objectives of this proposal are to perform preclinical studies from which information regarding the potential usefulness of hematoporphyrin photoradiation therapy (HpD PRT) in treating intraocular tumors can be obtained. The pigmented rabbit and amelanotic Greene melanoma (transplanted to the choroid) will serve as our animal and tumor model. In vivo distribution procedures will be employed to quantify HpD levels (using 3H-HpD) in both normal and malignant tissue of the rabbit eye. Preclinical toxicity studies will be performed to determine the maximum dosages of HpD PRT tolerated by normal ocular tissue. Fundus photography, fluorescein angiography, electroretinography and histopathological evaluation of treated eyes will be used to document acute and chronic lesions induced by HpD PRT. Histological assessment of treated tumors as well as tumor regrowth parameters and tumor cures will be methods used to evaluate the effectiveness of HpD PRT in treating ocular tumors.